1. Field of the Invention
The present invention relates to a data reproducing method and apparatus for reading data written in a data recording area of a recording medium while linking the data in predetermined units, and to a data recording method and apparatus for writing data to a data recording area of a recoding medium while linking the data in predetermined units.
2. Description of the Related Art
There has become popular a CD (compact disc) system in which an optical disc having an outside diameter of about 120 mm and a thickness of about 1.2 mm is used as a recording medium and a signal is read from, or written to, the optical disc by projecting a light converged by an objective lens onto a signal recording surface of the optical disc.
The CD system has initially been developed as a recording and playback system for digital audio data. As this technology has been accepted very widely, a wide variety of CD systems have so far been proposed for various applications.
Recently, the personal computers have been used as an information processing means in more and more ordinary households. Along with this tendency, a read-only optical disc called “CD-ROM (read-only memory)” has become popular to have recorded therein data handled in the personal computer.
Also, a recordable optical disc such as CD-R (recordable) and rewritable optical disc such as CD-RW (rewritable) have been developed and used in practice as optical discs interchangeable with the CD-ROM.
Data is recorded to the CD-R and CD-RW by the so-called “Track At Once” method by which data is written in units of a track, and the so-called “Packet Writing” method by which data is written in units of a packet which is a smaller unit than the track. When either the “Track At Once” or “Packet Writing” method is used to record data to the CD-R or CD-RW, a plurality of data linking blocks is provided between tracks or between packets, each being a unit in which data is continuously recorded, according to a predetermined linking rule. That is, in case data is recorded by the “Track At Once” method or “Packet Writing” method, it will be written with a plurality of data linking blocks appended at each unit of data which is to be continuously written.
The reason why the plurality of data linking blocks is appended between tracks or packets is that the CD-R and CD-RW adopt a convolution type cross coding method called “CIRC (cross interleave Reed-Solomon code)” and a data discontinuity takes place at a linking position because of the CIRC interleaving. That is, the data linking blocks are provided at a linking position of data as a guard area in which data missing is prevented in linking interleaved data to each other.
The additional or appended data linking blocks are meaningless as user data, and are removed when reading data. Therefore, the number of data linking blocks should desirably be as small as possible.
However, to properly link interleaved data for writing the data, or to positively detect, for reading the data, when such data linking blocks being meaningless as user data are reached or when there exist no more data linking blocks, the CD-R and CD-RW having the current format, for example, need as many as seven data linking blocks (14 kilobytes) for each unit of data to continuously be written, in practice.
Recently, optical discs having a higher recording density than the CD-R and CD-RW having the current format is under development. For a higher ability of burst error correction in such an optical disc having a high recording density, it has been studied to increase the interleaving length in the CIRC interleaving method. However, it is expected that with such an increased interleaving length, the linking of interleaved will influence so widely that an increased number of such data linking blocks will be required.